The present invention relates to a method and a system for carrying out control measurements on optical transmission paths. The present invention further relates to a method and a system for carrying out monitoring measurements on optical transmission paths.
In view of the high business use of optical transmission, the monitoring of the security of the transmission paths can be a critical ability. To provide anti-tapping and data-protection security, methods are known which assume substantial experimental outlay, for example, monitoring monomode fibers using cryptologic such as quantum cryptologic methods, or utilizing Raman or Brillouin backscattering. These very expensive methods may document the considerable interest that exists in achieving unaffected, trouble-free communication transmission.
In addition, regular control and checking of optical transmission paths are needed to maintain proper telecommunications operation via optical transmission paths. Special cable fibers or glass fibers can require continuous monitoring. Thus, the operational path must be able to be controlled in parallel with the normal telecommunications operation, without disturbing this operation.
French Patent No. 2 739 992, describes a monitoring system based on the analysis of reflected signals for an optical telecommunications network. This monitoring system makes use of Bragg gratings.
European Patent No. 0 432 734, describes a device and a method for detecting defective locations or damage on an optical transmission system.
Those systems appear to work with an additionally launched signal. The launched signal can be selectively reflected after propagating through part of or all of the entire transmission path and whose wavelength is different from the wavelength of the useful information to be transmitted.
However, those known systems are not suited for utilizing the chromatic dispersion that the signals propagating through the fiber are subject to in order to control the optical transmission path. Further, those known systems are not suited for utilizing the polarization state that the signals exhibit after propagating through the fiber in order to monitor the optical transmission path.
The present invention provides a method and a system for carrying out control measurements during normal telecommunications operation, without adversely affecting the same, and the chromatic dispersion, which the signals propagating through the fiber are subjected to, is utilized to control the optical transmission path.
The present invention further provides a method and a system for carrying out monitoring measurements during normal telecommunications operation, without adversely affecting the same, and the polarization state exhibited by the signals after propagating through the fiber and their propagation time are analyzed to monitor the optical transmission path.
The present invention further provides minimizing the technical outlay to a minimum. The method and the system, respectively, should make it possible to acquire important operating parameters for the transmission path and, additionally, to reliably detect any tampering with the transmission path, especially tapping of or eavesdropping on the data communication traffic.